As a method for forming a film on a substrate, for example, a semiconductor wafer (hereinafter, referred to as a “wafer”), a so-called atomic layer deposition (ALD) method or multi-layer deposition (MLD) method is known in which a plurality of kinds of gases reacting with each other are sequentially supplied to the wafer.
Various gas supply mechanisms that supply the reaction gases to the wafer are proposed in such a film-forming method. For example, Patent Document 1 discloses a film-forming apparatus in which a cylindrical intermediate dispersion body is disposed in a central portion of a dispersion guide having an inclined structure which is widened from the center toward the outer circumference, and gases are introduced into the dispersion guide through a plurality of openings formed in a side surface and a bottom surface of the intermediate dispersion body.
Patent Document 2 discloses a vapor deposition apparatus in which two horns are disposed in a nested form in which the horns have inclined structures which are widened from the center toward the outer circumference with different inclinations, and gases are introduced downward from a space surrounded by the inner horn and a space surrounded by the inner horn and the outer horn, respectively.
In some cases, it has been requested that a film deposited in a nanometer order have uniformity in a wafer plane (e.g., an M-m value to be described later) within about 5%. However, it is difficult to realize in-plane uniformity with such a high precision in a method in which reaction gases are supplied from the central portions of the dispersion guide and the horns in a concentrated manner as disclosed in Patent Documents 1 and 2.